Mathew,
couple of things come to mind here.
If you getting less power with duplexer it could be due to duplexer not 50 Ohms giving higher SWR and PA is probably folding back. Also what type of watt meter. Hope something like a Bird. Cheap meters can give bad reading depending on load. Also if the duplexer is not tuned properly or cable lengths could cause such a problem.
I always check the SWR between duplexer and tx, not just between antenna and duplexer. I also like checking SWR with a source on rx freq on duplexer input/output port and load on rx port. Loading on the bench can give different results than the actually installation.
When I tune duplexers I also put load on all open ports such as when tuning tx side put load on rx port (don't use a receiver, but dummy load).
73, ron, n9ee/r
73, ron, n9ee/r
Ron Wright
Ron is the owner of Micro Computer Concepts, a manufacture of repeaters and repeater controllers since 1988.
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----- Original Message -----From: Mathew QuaifeSent: 7/8/2005 10:42:19 AMSubject: RE: [Repeater-Builder] Repeater heard on Aviation Channel! HELPOk, this brought up a good point. Just for sakes I took the watt meter, from the amp into a 50 ohm load, I get 140 watts out, into the duplexer's I get 70 watts out, something there has changed. With a 2.2 dB insertion loss, I should be getting right about 90 watts out if I did the math right? Anyone get anything different, if so, give me the math figures so I can check it again.Mathew
Dave VanHorn <[EMAIL PROTECTED]> wrote:
This reminds me of an incident many years ago when Industry Canada (then called DOC) contacted us re a ham 2 meter mobile interfering with aircraft communications. To make a long story short, the local ham wanted more power out of his transmitter and had physically adjusted the low pass filter (the push and squeeze method) for more output power. He also defeated the purpose of the filter and all kinds of crap was getting through as well. His Watt meter showed some more power but since it is essentially a non frequency selective device, it didnt care what was going through.
Sad.. Very sad. :)
Which brings up another story of a tech who could not match a ¼ wave mobile antenna to a transmitter no matter how he cut the whip. Again the Spec A showed that the TX was badly spurious and the antenna was showing lots of reflected power because of it. Once the PA was tuned properly so that the spurious signals disappeared, the antenna matched just fine. Sometimes you have to use the proper test equipment to see what is going on.
Very very true! I spend a lot of time and money picking up test equipment for that reason. If I can't see, I can't work.
I have been reading these post for a couple of days now and seen in the original post that you are loosing 110 watts in the duplexer. Maybe Im the only one that thanks this may have something to do with the problem.
Yikes, I didn't catch that in the original read either! That is VERY significant! 1-1.5dB maybe, but not >3dB!
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